Apparatus and method for providing streaming content using representations

ABSTRACT

A method and apparatus for an adaptive Hypertext Transfer Protocol (HTTP) streaming service using metadata of media content are provided. The media content may include a sequence of one or more periods. Each of the periods may include one or more representations. The metadata may include information used to describe a relationship between the representations, and include information for terminals having different display bit depths.

TECHNICAL FIELD

The present invention relates to a technology for providing streaming content, and more particularly, to an apparatus and method for providing media content using a representation of the media content.

BACKGROUND ART

Streaming is one of schemes for transmitting and playing back multimedia content such as sounds, moving images, and the like. A client may play back content while receiving the content through the streaming.

An adaptive streaming service refers to providing a streaming service using a communication scheme with a request of a client and a response of a server in response to the request.

The client may request a media sequence suitable for an environment of the client (for example, a transmission channel of the client), using the adaptive streaming service. The server may provide a media sequence matched to the request of the client among media sequences with various qualities that are included in the server.

The adaptive streaming service may be provided based on various protocols. A Hypertext Transfer Protocol (HTTP) adaptive streaming service refers to an adaptive streaming service provided based on an HTTP. A client of the HTTP adaptive streaming service may receive content from a server using the HTTP, and may transmit a request associated with a streaming service to the server.

DISCLOSURE OF INVENTION Technical Goals

An aspect of the present invention provides an apparatus and method that may play back media content using representations including accessibility information.

Another aspect of the present invention provides an apparatus and method that may play back media content using information used to describe a relationship between representations of the media content.

Still another aspect of the present invention provides an apparatus and method that may play back media content using information of different representations for terminals having different display bit depths.

Technical Solutions

According to an aspect of the present invention, there is provided a method for providing media content, the method including: receiving metadata of media content, the metadata including one or more periods; accessing segments of the media content based on information provided by the metadata; and decoding and rendering data of the media content that is included in the segments, wherein each of the periods includes one or more representations of the media content, and wherein each of the representations includes information used to support disabled users who have difficulties in perceiving the media content.

A media component of each of the representations may be enhanced to cope with a problem of a disabled user, and enhancement of the media component may include at least one of adjustment of a contrast and adjustment of a colour.

The information included in each of the representations may indicate an intended use of each of the representations, and the intended use may include at least one of a sign language, a subtitle, a caption, and a description.

The information included in each of the representations may indicate an attribute providing a reference to an external Moving Picture Experts Group (MPEG)-21 Digital Item Adaptation (DIA).

According to another aspect of the present invention, there is provided a method for providing media content, including: receiving metadata of media content, the metadata including one or more periods; accessing segments of the media content based on information provided by the metadata; and decoding and rendering data of the media content that is included in the segments, wherein each of the periods includes one or more representations of the media content, and wherein the metadata includes an attribute describing a relationship between the representations.

A first representation among the representations may include an attribute indicating a list of a part of the representations, and may be used together with a representation among the part of the representations.

The first representation may be a representation used for audio description.

Each of the part of the representations may be a representation used for a video component.

A first representation among the representations may include an attribute indicating a list of a part of the representations.

A representation among the part of the representations may be replaced by the first representation.

According to still another aspect of the present invention, there is provided a method for providing media content, including: receiving metadata of media content, the metadata including one or more periods; accessing segments of the media content based on information provided by the metadata; and decoding and rendering data of the media content that is included in the segments, wherein each of the periods includes one or more representations of the media content, and wherein each of the representations includes a bit depth attribute used to select different representations for terminals having different display bit depths.

The bit depth attribute may indicate a number of bits used to represent a luma/chroma sample of visual content.

According to yet another aspect of the present invention, there is provided a terminal including: an access engine to receive metadata of media content, to receive segments of the media content based on information provided by the metadata, and to decode data of the media content that is included in the segments, the metadata including one or more periods; and a media engine to receive the data of the media content from the access engine, and to output the media content, wherein each of the periods includes one or more representations of the media content, and wherein each of the representations includes information used to support disabled users who have difficulties in perceiving the media content.

According to a further aspect of the present invention, there is provided a terminal including: an access engine to receive metadata of media content, to receive segments of the media content based on information provided by the metadata, and to decode data of the media content that is included in the segments, the metadata including one or more periods; and a media engine to receive the data of the media content from the access engine, and to output the media content, wherein each of the periods includes one or more representations of the media content, and wherein the metadata includes an attribute describing a relationship between the representations.

According to a further aspect of the present invention, there is provided a terminal including: an access engine to receive metadata of media content, to receive segments of the media content based on information provided by the metadata, and to decode data of the media content that is included in the segments, the metadata including one or more periods; and a media engine to receive the data of the media content from the access engine, and to output the media content, wherein each of the periods includes one or more representations of the media content, and wherein each of the representations includes a bit depth attribute used to select different representations for terminals having different display bit depths.

Effect of the Invention

According to embodiments of the present invention, it is possible to play back media content using representations including accessibility information.

Additionally, according to embodiments of the present invention, it is possible to play back media content using information used to describe a relationship between representations of the media content.

Furthermore, according to embodiments of the present invention, it is possible to play back media content using information of different representations for terminals having different display bit depths.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a Dynamic Adaptive Streaming over HTTP (DASH) high-level data model.

FIG. 2 is a signal flowchart illustrating a content processing method according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating categories of signaling information according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a hierarchy of content division and levels of signaling information according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of a terminal according to an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.

The entire document “Dynamic Adaptive Streaming over HTTP (DASH)—Part 1: Media presentation description and segment format” of ISO/IEC DIS 23009-1 published on Aug. 30, 2011, will be cited as references in the present application, and will used to describe the following embodiments.

Hereinafter, embodiments of the present invention will be further described with reference to the accompanying drawings, however, there is no limitation to the embodiments of the present invention. Like reference numerals refer to the like elements throughout.

The terms “specify,” “indicate,” and “mean” used herein may have the same meaning. Additionally, the terms “Uniform Resource Locator (URL)” and “Uniform Resource Identifier (URI)” used herein may have the same meaning, and may be interchangeable.

When indexes for a specific element are from 1 to N, or from 0 to N, the number of specific elements may be one or more. N may be an integer equal to or greater than 0.

Hereinafter, examples of terms used in embodiments will be described.

-   -   DASH may specify formats that enable 1) delivery of media         content from an HTTP server to an HTTP client, and enable 2)         caching of content by standard HTTP cashes. The formats may         include, for example, an Extensible Markup Language (XML)         format, or a binary format.     -   Media content may be a single media content period, or a         contiguous sequence of media content periods. Hereinafter, media         content, media, and content may be used as interchangeable         terms. Media content may be a set of media content components         having a common timeline, for example audios, videos, or timed         texts. Additionally, media components may have relationships on         how the media components may be presented (for example,         individually, jointly, or mutually exclusive) as programs or         movies. Media content may be content on demand, or live content.

Content may be divided into one or more intervals. In other words, the content may include one or more intervals. Hereinafter, an interval and a period may be used as interchangeable terms. The term period may be used as a term in 3^(rd) Generation Partnership Project (3GPP) adaptive HTTP streaming. In other words, a period may be an interval of a media presentation. A continuous sequence of all periods may constitute the media presentation.

One or more intervals may be a basic unit. One or more intervals may be described by signaling metadata. In other words, metadata may describe each of the one or more intervals. The metadata may be a Media Presentation Description (MPD) that will be described later.

-   -   A media content component may be a continuous component of media         content with an assigned media component type. A media content         component may be encoded individually into a media stream. A         media component may be an encoded version of individual media         types, such as audios, videos, or timed texts with specific         attributes, for example bandwidths, languages, or resolutions.     -   A media stream may be an encoded version of a media content         component     -   A media component type may be a single type of media content,         such as audio, video, or text.     -   A media presentation may be a collection of data used to         establish a bounded or unbounded presentation of media content.         The media presentation may be a collection of data that is         accessible to a DASH client to provide a streaming service to a         user. An MPD may be described by an MPD. The media presentation         may be a collection of data that is accessible to a DASH client         to provide a streaming service to a user.     -   An MPD may be a formalized description for a media presentation         to provide a streaming service. The MPD may be a document         containing metadata required by a DASH client, to provide a user         with a streaming service, and to construct appropriate HTTP-URLs         to access segments. The media presentation may be described by         an MPD including possible updates of the MPD.

An MPD may be a document containing metadata requested to a DASH client to construct appropriate HTTP-URLs in order to 1) access segments and to 2) provide a user with a streaming service. The HTTP-URLs may be absolute or relative. The MPD may be an XML-document.

The MPD may define a format to announce resource identifiers for segments. The MPD may provide a context for identified resources within the media presentation. The resource identifiers may be HTTP-URLs. URLs may be restricted by a byte range attribute.

-   -   A period may be an interval of a media presentation. A         continuous sequence of all periods may constitute the media         presentation. In other words, the media presentation may include         one or more periods. Alternatively, the media presentation may         include a sequence of one or more periods.     -   A representation may be a collection and encapsulation of one or         more media streams in a delivery format, and may be associated         with descriptive metadata. The representation may be a         structured collection of one or more media components within a         single period. In other words, the representation may be one of         alternative choices of a complete set or subset of media content         components forming media content during a defined period. The         representation may include one or more media streams.

A representation may start at a beginning point of a period (namely, a period including the representation), and may continue to an ending point of the period.

A representation may be one of alternative choices of the media content or a subset of the media content typically differing by the encoding choice, for example by a bitrate, a resolution, a language, a codec, and the like.

An MPD (or an MPD element) may provide descriptive information that enables a client to select one or more representations.

Hereinafter, a representation and a media representation may be used as interchangeable terms.

Two or more sets of segments corresponding to a single interval may exist. Each of the sets may be called a representation, or an alternative.

-   -   A segment may be a smallest addressable unit in an MPD with a         defined format. Hereinafter, a segment and a media segment may         be used as interchangeable terms.

Each interval may be divided into segments. Hereinafter, a segment and a fragment may be used as interchangeable terms. The term segment may be used as a term of 3GPP adaptive HTTP streaming.

A segment may mean an entity body of a response to an HTTP/1.1 GET request for an HTTP-URL, for example as defined in RFC 2616, (or a GET request for a part indicated by a byte range).

A terminal may play back media content using received bytes (namely, a segment).

-   -   A sub-segment may mean a smallest unit within segments that may         be indexed by a segment index at a segment level.     -   A sub-representation may be a part of a representation described         in an MPD that is present in the entire period.     -   A Random Access Point (RAP) may be a specific location in a         media segment. The RAP may be identified as a location in which         playback may be started continuously from a location of the RAP         using only information included in a media segment.

The DASH may provide a media-streaming model for delivery of media content. A client may exclusively control a session of the delivery. Clients may request data using the HTTP protocol from standard web servers that do not have DASH-specific capabilities. Accordingly, the DASH standard may focus on data formats used to provide a DASH media presentation.

A collection of encoded and deliverable versions of media content, and an appropriate description of the versions may form a media presentation. Media content may include one or more contiguous media content periods in time. Each media content period may include one or more media content components, for example audio components in various languages and a video component. A media content component type may be assigned to each media content component, and may include, for example, audio or video.

Each media content component may have one or more encoded versions. An encoded version of a media content component may be referred to as a “media stream.” Each media stream may inherit attributes of media content used to encode media content, a media content period, or a media stream. Additionally, to each media stream, properties of an encoding process, such as sub-sampling, codec parameters, encoding bitrate, and the like, may be assigned. Accordingly, metadata may be relevant for static and dynamic selection of media content components and media streams.

FIG. 1 is a diagram illustrating a DASH high-level data model.

A DASH may be based on a hierarchical data model, as shown in FIG. 1.

A DASH media presentation may be described by an MPD document. The MPD may describe a sequence of periods in time. The sequence of the periods may form a media presentation. A period may typically represent a media content period during which a consistent set of encoded versions of media content is available. In other words, during a single period, bitrates, languages, captions, subtitles, and the like, may not be changed.

A period may include one or more adaptation sets. An adaptation set may represent a set of interchangeable encoded versions of one or more media content components. For example, an adaptation set for a main video component, and a separate adaptation set for a main audio component may exist. For example, when there are other available materials, for example captions or audio descriptions, the other available materials may each have a separate adaptation set.

An adaptation set may include one or more representations. A representation may describe a deliverable encoded version of one or more media content components. A representation may include one or more media streams. A single representation within an adaptation set may be sufficient to render the media content components included in the single representation. Typically, a client may switch from one representation to another representation during a period, in order to adapt to network conditions or other factors. The client may also ignore representations that rely on codecs or other rendering technologies that are not supported by the client, or that are otherwise unsuitable.

Within a representation, the content may be divided in time into segments. In other words, the representation may include one or more segments. A segment may be a basic unit of data that is advertised in an MPD. A URL may be provided for each segment. The providing of the URL may indicate that a segment is the largest unit of data that may be retrieved with a single HTTP request. The MPD may include a byte range of the URL, with the URL. Accordingly, the segment may be included in a byte range of other larger resources.

Hereinafter, a relationship between components of the above-described data model will be described.

-   -   An MPD may include a sequence of one or more periods.     -   Each of the periods may include one or more adaptation sets.         When an adaptation set includes one or more media content         components, each of the media content components may be         individually defined.     -   Each of the adaptation sets may include one or more         representations.     -   Each of the representations may include one or more         sub-representations.     -   Each of the representations may include one or more segments.     -   Segments may include media data, and/or metadata to access,         decode, and present media content including the segments.     -   Adaptation sets, representations and sub-representations may         share common attributes and elements.     -   Each of the segments may include one or more subsegments.

An MPD document indicating an MPD may include an element “MPD.”

The following Table 1 shows an XML schema of MPD.

TABLE 1 <?xml version=“1.0” encoding=“UTF-8”?> <xs:schema targetNamespace=“urn:mpeg:DASH:schema:MPD:2011”  attributeFormDefault=“unqualified”  elementFormDefault=“qualified”  xmlns:xs=“http://www.w3.org/2001/XMLSchema”  xmlns:xlink=“http://www.w3.org/1999/xlink”  xmlns=“urn:mpeg:DASH:schema:MPD:2011”>  <xs:import namespace=“http://www.w3.org/1999/xlink”   schemaLocation=“http://www.w3.org/1999/xlink.xsd”/>  <xs:annotation>   <xs:appinfo>Media Presentation Description</xs:appinfo>   <xs:documentation xml:lang=“en”>    This Schema defines the Media Presentation Description for    MPEG-DASH.   </xs:documentation>  </xs:annotation>  <!-- MPD: main element -->  <xs:element name=“MPD” type=“MPDtype”/>  ... </xs:schema>

Table 1 shows an initial part of the XML schema of the MPD. The initial part may include namespace and other definitions.

A mechanism for referencing remote elements from a local MPD may be defined. A subset of World Wide Web Consortium (W3C) XLINK simple links may be defined, consisting of 1) restricted syntax and semantics, and 2) a processing model.

XLINK attributes used in a part of ISO/IEC 23009 are provided as follows:

-   -   “xlink:type” may define a type of W3C XLINK that is being used.     -   “xlink:href” may identify a remote element using a URI, as         defined in IETF RFC 3986.     -   “xlink: show” may define a desired behaviour of a remote element         once dereferenced from within an MPD, as defined in W3 C XLINK.     -   “xlink:actuate” may define a desired timing of dereferencing a         remote element from within an MPD, as defined in W3 C XLINK.

The following Table 2 shows an XML schema of XLINK.

TABLE 2 <?xml version=‘1.0’ encoding=‘UTF-8’?> <xs:schema xmlns:xs=“http://www.w3.org/2001/XMLSchema”   targetNamespace=“http://www.w3.org/1999/xlink”   xmlns:xlink=“http://www.w3.org/1999/xlink”>   <xs:attribute name=“type” type=“xs:token” fixed=“simple”/>   <xs:attribute name=“href” type=“xlink:hrefType”/>   <xs:simpleType name=“hrefType”>   <xs:restriction base=“xs:anyURI”/>   </xs:simpleType>     <xs:attribute name=“show” type=“xs:token” fixed=“embed”/>   <xs:attribute  name=“actuate”  type=“xlink:actuateType” default=“onRequest”/>   <xs:simpleType name=“actuateType”>     <xs:restriction base=“xs:token”>       <xs:enumeration value=“onLoad”/>       <xs:enumeration value=“onRequest”/>     </xs:restriction>   </xs:simpleType> </xs:schema>

In the schema, a namespace, a name, a type, and a default value of each element or each attribute may be described. Additionally, a hierarchical relationship between elements and attributes may be described.

Rules applied to process URI references within the attribute “xlink:href” are provided as follows:

-   -   URI references to remote elements that cannot be resolved may be         treated as invalid references, and may invalidate the MPD.     -   URI references to remote elements that are inappropriate targets         for a given reference may be treated as invalid references, and         may invalidate the MPD.     -   URI references that directly or indirectly reference themselves         may be treated as invalid circular references, and may         invalidate the MPD.     -   A reference to a remote element may be an HTTP-URL.     -   When a URI reference is relative, a reference resolution may be         applied.

Semantics of the element “MPD” are described as follows:

1) The element “MPD” may have the following attributes:

-   -   “id” may specify an identifier for a media presentation. “id”         may be an identifier that is unique within a scope in which the         media presentation is published.     -   “type” may specify whether the MPD may be updated.     -   “mediaPresentationDuration” may specify a duration of the entire         media presentation. When “mediaPresentationDuration” is absent,         the duration of the media presentation may be unknown.     -   “maxSegmentDuration” may specify a maximum duration of a segment         in a representation in the media presentation.

2) The element “MPD” may have the following elements:

-   -   “ProgramInformation” may have an index of 0 to N, and may         specify descriptive information about a program. Having an index         of N may indicate that a number of instances of an element may         be unbounded. Having an index of 0 may indicate that an element         may be optional. Having an index of 1 may indicate that an         element is mandatory. In other words, a range of index may         represent occurrence or cardinality.     -   “BaseURL” may have an index of 0 to N, and may specify a base         URL that may be used for reference resolution and alternative         URL selection.     -   “Location” may have an index of 0 to N, and may specify a         location at which the MPD is available.     -   “Period” may have an index of 1 to N, and may specify         information of a period.     -   “Metrics” may have an index of 0 to N, and may specify DASH         metrics.

The following Table 3 shows an XML syntax of the element “MPD”.

TABLE 3 <!-- MPD Type --> <xs:complexType name=“MPDtype”>  <xs:sequence>   <xs:element name=“ProgramInformation” type=“ProgramInformationType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“BaseURL” type=“BaseURLType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Location” type=“xs:anyURI” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Period” type=“PeriodType”   maxOccurs=“unbounded”/>   <xs:element name=“Metrics” type=“MetricsType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:any namespace=“##other” processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“id” type=“xs:string”/>  <xs:attribute name=“profiles” type=“xs:string”/>  <xs:attribute name=“type” type=“PresentationType” default=“static”/>  <xs:attribute name=“availabilityStartTime” type=“xs:dateTime”/>  <xs:attribute name=“availabilityEndTime” type=“xs:dateTime”/>  <xs:attribute name=“mediaPresentationDuration” type=“xs:duration”/>  <xs:attribute name=“minimumUpdatePeriod” type=“xs:duration”/>  <xs:attribute name=“minBufferTime” type=“xs:duration”  use=“required”/>  <xs:attribute name=“timeShiftBufferDepth” type=“xs:duration”/>  <xs:attribute name=“suggestedPresentationDelay” type=“xs:duration”/>  <xs:attribute name=“maxSegmentDuration” type=“xs:duration”/>  <xs:attribute name=“maxSubsegmentDuration” type=“xs:duration”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType> <!-- Presentation Type enumeration --> <xs:simpleType name=“PresentationType”>  <xs:restriction base=“xs:string”>   <xs:enumeration value=“static”/>   <xs:enumeration value=“dynamic”/>  </xs:restriction>     </xs:simpleType>

A media presentation may include one or more periods. Each of the periods may be defined by the element “Period” in the element “MPD.”

Periods may be classified into regular periods and early available periods. Additionally, a PeriodStart time of a regular period may be defined as follows:

-   -   When attribute “start” is included in the element “Period”, a         period may be a regular period, and the PeriodStart time may be         equal to a value of the attribute “start”.     -   When the attribute “start” is absent, but a previous element         “Period” includes attribute “duration”, a period may be a         regular period. The start time of the period “PeriodStart” may         be a sum of a start time of a previous period and a value of the         attribute “duration” of the previous period.     -   1) When the attribute “start” is absent, 2) when the element         “Period” is the first in the MPD, and 3) when the attribute         “type” of the MPD is “static,” the PeriodStart time may be set         to “0.”     -   1) When the attribute “start” is absent, 2) when a previous         element “Period” does not include attribute “duration”, or when         the element “Period” is the first in the MPD, and 3) when the         attribute “type” of the MPD is “dynamic,” a period may be an         early available period.

Semantics of the element “Period” are described as follows:

1) The element “Period” may have the following attributes:

-   -   “xlink:href” may specify a reference to an external element         “Period.”     -   “xlink:actuate” may specify processing instructions.         “link:actuate” may have a value of either “onload” or “on         Request.     -   “id” may specify an identifier of a period. “id” may be a unique         identifier within a scope of a media presentation.     -   “start” may specify a PeriodStart time of a period. The         PeriodStart time may be used as an anchor to determine an MPD         start time of each media segment, as well as to determine a         presentation time of each access unit in a media presentation         timeline.     -   “duration” may specify a duration of a period to determine a         PeriodStart time of a next period.

2) The element “Period” may have the following elements:

-   -   “BaseURL” may have an index of 0 to N, and may be used for         reference resolution and alternative URL selection.     -   “AdaptationSet” may have an index of 1 to N, and may specify         information of an adaptation set.     -   “Subset” may have an index of 0 to N, and may specify a subset.

The following Table 4 shows an XML syntax of the element “Period.”

TABLE 4 <!-- Period --> <xs:complexType name=“PeriodType”>  <xs:sequence>   <xs:element name=“BaseURL” type=“BaseURLType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“SegmentBase” type=“SegmentBaseType”   minOccurs=“0”/>   <xs:element name=“SegmentList” type=“SegmentListType”   minOccurs=“0”/>   <xs:element name=“SegmentTemplate” type= “SegmentTemplateType” minOccurs=“0”/>   <xs:element name=“AdaptationSet” type=“AdaptationSetType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Subset” type=“SubsetType” minOccurs=“0” maxOccurs=“unbounded”/>  <xs:any namespace=“##other” processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute ref=“xlink:href”/>  <xs:attribute ref=“xlink:actuate” default=“onRequest”/>  <xs:attribute name=“id” type=“xs:string” />  <xs:attribute name=“start” type=“xs:duration”/>  <xs:attribute name=“duration” type=“xs:duration”/>  <xs:attribute name=“bitstreamSwitching” type=“xs:boolean”  default=“false”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType>

Each period may include one or more adaptation sets. Each of the adaptation sets may be described by element “AdaptationSet” included in the element “Period.”

An adaptation set may include alternate encodings of one or more media content components. Each of the alternate encodings may be included in a representation. All representations included in a single adaptation set may represent the same media content components, and may include one or more media streams that are determined to be perceptually equivalent.

One or more representations may be arranged in an adaptation set based on properties of media content components present in the representations. The properties of the media content components may include 1) a language described by attribute “lang”, 2) a media component type described by attribute “contentType”, 3) a picture aspect ratio described by attribute “par”, 4) a role property described by element “Role”, 5) an accessibility property described by element “Accessibility”, 6) a viewpoint property as described by element “ViewPoint”, 7) a rating property described by element “Rating,” and the like.

The element “AdaptationSet” may include default values for elements and attributes associated with one or more representations included in an adaptation set. Hereinafter, a list of possible present elements and attributes that are common to the elements “AdaptationSet” and “Representation” will be described.

The element “AdaptationSet” may support description of ranges for attributes “bandwidth,” “width,” “height” and “framerate” that are associated with one or more representations included in an adaptation set. The description may provide a summary of all values for all of the representations included in the adaptation set. The representations included in the adaptation set may not have values outside the ranges defined in the adaptation set.

Adaptation sets may be classified into groups, using attribute “group”.

Semantics of the element “AdaptationSet” are described as follows:

1) The element “AdaptationSet” may have the following attributes:

-   -   “xlink:href” may specify a reference to external element         “AdaptationSet.”     -   “xlink:actuate” may specify processing instructions.         “link:actuate” may have a value of either “onload” or “on         Request.     -   “id” may specify an identifier of an adaptation set in the scope         of the period. “id” may be a unique identifier within a scope         including the containing Period. “id” may not exist in a remote         element.     -   “group” may specify an identifier of a group that is unique in         the scope of the period.     -   “lang” may declare language code(s) of an adaptation set. Syntax         and semantics based on IETF RFC 5646 may be used.     -   “contentType” may specify a media content component type of an         adaptation set. “type” may be a content-type of top-level.         “type” may be defined in RFC1521.     -   “par” may specify a picture aspect ratio. “par” may include two         integers. When “par” is present, attributes “width” and “height”         for representations may also be present.     -   “minBandWidth” may specify a minimum value of the attribute         “bandwidth” in all representations in an adaptation set.     -   “maxBandWidth” may specify a maximum value of the attribute         “bandwidth” in all representations in an adaptation set.     -   “minWidth” may specify a minimum value of the attribute “width”         in all representations in an adaptation set.     -   “maxWidth” may specify a maximum value of the attribute “width”         in all representations in an adaptation set.     -   “minHeight” may specify a minimum value of the attribute         “height” in all representations in an adaptation set.     -   “maxHeight” may specify a maximum value of the attribute         “height” in all representations in an adaptation set.     -   “minFrameRate” may specify a minimum value of the attribute         “frameRate” in all representations in an adaptation set.     -   “maxFrameRate” may specify a maximum value of the attribute         “frameRate” in all representations in an adaptation set.

2) The element “AdaptationSet” may have the following elements:

-   -   “Accessibility” may have an index of 0 to N, and may specify         information on an accessibility scheme.     -   “Role” may have an index of 0 to N, and may specify information         on a role annotation scheme.     -   “Rating” may have an index of 0 to N, and may specify         information on a rating scheme.     -   “Viewpoint” may have an index of 0 to N, and may specify         information on a viewpoint annotation scheme.     -   “ContentComponent” may have an index of 0 to N, and may specify         properties of a media content component included in an         adaptation set.     -   “BaseURL” may have an index of 0 to N, and may be used for         reference resolution and alternative URL selection.     -   “Representation” may have an index of 0 to N, and may specify a         representation. At least one representation element may be         included in each adaptation set. “Representation” may be a part         of a remote element.

The following Table 5 shows an XML syntax of the element “AdaptationSet.”

TABLE 5 <!-- Adaptation Set --> <xs:complexType name=“AdaptationSetType”>  <xs:complexContent>   <xs:extension base=“RepresentationBaseType”>    <xs:sequence>     <xs:element name=“Accessibility” type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“Role” type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“Rating” type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“Viewpoint” type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“ContentComponent” type=“ContentComponentType” minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“BaseURL” type=“BaseURLType” minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“SegmentBase” type=“SegmentBaseType” minOccurs=“0”/>     <xs:element name=“SegmentList” type=“SegmentListType” minOccurs=“0”/>     <xs:element name=“SegmentTemplate” type=“SegmentTemplateType” minOccurs=“0”/>     <xs:element name=“Representation” type=“RepresentationType” minOccurs=“0” maxOccurs=“unbounded”/>    </xs:sequence>    <xs:attribute ref=“xlink:href”/>    <xs:attribute ref=“xlink:actuate” default=“onRequest”/>    <xs:attribute name=“id” type=“xs:unsignedInt”/>    <xs:attribute name=“group” type=“xs:unsignedInt”/>    <xs:attribute name=“lang” type=“xs:language”/>    <xs:attribute name=“contentType” type=“xs:string”/>    <xs:attribute name=“par” type=“xs:string”/>    <xs:attribute name=“minBandwidth” type=“xs:unsignedInt”/>    <xs:attribute name=“maxBandwidth” type=“xs:unsignedInt”/>    <xs:attribute name=“minWidth” type=“xs:unsignedInt”/>    <xs:attribute name=“maxWidth” type=“xs:unsignedInt”/>    <xs:attribute name=“minHeight” type=“xs:unsignedInt”/>    <xs:attribute name=“maxHeight” type=“xs:unsignedInt”/>    <xs:attribute name=“minFrameRate” type=“xs:string”/>    <xs:attribute name=“maxFrameRate” type=“xs:string”/>    <xs:attribute name=“segmentAlignment” type=“ConditionalUintType” default=“false”/>    <xs:attribute name=“subsegmentAlignment” type=“ConditionalUintType” default=“false”/>    <xs:attribute name=“subsegmentStartsWithSAP” type=“SAPType” default=“0”/>    <xs:attribute name=“bitstreamSwitching” type=“xs:boolean”/>   </xs:extension>  </xs:complexContent> </xs:complexType> <!-- Conditional Unsigned Integer (unsignedInt or boolean) --> <xs:simpleType name=“ConditionalUintType”>  <xs:union memberTypes=“xs:unsignedInt xs:boolean”/> </xs:simpleType>

An adaptation set may include one or more media content components. Properties of each of the media content components may be described by the element “ContentComponet.” When a single media content component is included in an adaptation set, properties of the media content component may be described directly by the element “AdaptationSet.”

Semantics of the element “ContentComponent” are described as follows:

1) The element “ContentComponent” may have the following attributes:

-   -   “id” may specify an identifier of a media component. “id” may be         unique within a scope of an adaptation set.     -   “lang” may declare language code(s) of a media content         component. Syntax and semantics based on IETF RFC 5646 may be         used.     -   “contentType” may specify a type of a media content component. A         value of the top-level content-type, namely “type”, may be         defined in RFC1521.     -   “par” may specify a picture aspect ratio. “par” may include two         integers. When     -   “par” is present, attributes “width” and “height” for         representations may also be present.

2) The element “ContentComponent” may have the following elements:

-   -   “Accessibility” may have an index of 0 to N, and may specify         information on an accessibility scheme.     -   “Role” may have an index of 0 to N, and may specify information         on a role annotation scheme.     -   “Rating” may have an index of 0 to N, and may specify         information on a ration scheme.     -   “Viewpoint” may have an index of 0 to N, and may specify         information on a viewpoint annotation scheme.

The following Table 6 shows an XML syntax of the element “ContentComponent.”

TABLE 6 <!-- Content Component --> <xs:complexType name=“ContentComponentType”>  <xs:sequence>   <xs:element name=“Accessibility”  type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element   name=“Role” type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element  name=“Rating”  type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element  name=“Viewpoint”  type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:any  namespace=“##other”  processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“id” type=“xs:unsignedInt”>  <xs:attribute name=“lang” type=“xs:language”/>  <xs:attribute name=“contentType” type=“xs:string”/>  <xs:attribute name=“par” type=“xs:string”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType>

Representations may be described by the element “Representation.” The element “AdaptationSet” may include one or more elements “Representation.”

A representation may be one of alternative choices of a complete set or subset of media content components forming media content during a defined period.

A representation may start at the start of the PeriodStart of a period, and may continue to the end of the period. In other words, the end of the period may be the start of a next period, or the end of a media presentation.

Each representation may include one or more media streams. Each of the media streams may be an encoded version of a media content component.

A representation may include one or more segments.

Semantics of the element “Representation” are described as follows:

1) The element “Representation” may have the following attributes:

-   -   “id” may specify an identifier of a representation. When a         representation is functionally different from another         representation within the same period, “id” may be unique within         the scope of the period. “id” may not include whitespace         characters.     -   “bandwidth” may specify a bound on a data rate and data rate         variation of a representation.     -   “qualityRanking” may specify, a quality ranking of a         representation, relative to other representations in the same         adaptation set.     -   “dependencyID” may specify all complementary representations         that depend on in decoding and/or presentation process.         “dependencyID” may be a whitespace-separated list of values of         “id.”

2) The element “Representation” may have the following elements:

-   -   “BaseURL” may have an index of 0 to N, and may be used for         reference resolution and alternative URL selection.     -   “SubRepresentation” may have an index of 0 to N, and may specify         information on a sub-representation that is embedded in a         representation. “SubRepresentation” may be used for reference         resolution and alternative URL selection.

The following Table 7 shows an XML syntax of the element “AdaptationSet.”

TABLE 7 <!-- Representation --> <xs:complexType name=“RepresentationType”>  <xs:complexContent>   <xs:extension base=“RepresentationBaseType”>    <xs:sequence>     <xs:element name=“BaseURL” type=“BaseURLType” minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“SubRepresentation” type=“SubRepresentationType” minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“SegmentBase” type=“SegmentBaseType” minOccurs=“0”/>     <xs:element name=“SegmentList” type=“SegmentListType” minOccurs=“0”/>     <xs:element name=“SegmentTemplate” type=“SegmentTemplateType” minOccurs=“0”/>    </xs:sequence>    <xs:attribute name=“id” type=“xs:string” use=“required”/>    <xs:attribute name=“bandwidth” type=“xs:unsignedInt”    use=“required”/>    <xs:attribute name=“qualityRanking” type=“xs:unsignedInt”/>    <xs:attribute name=“dependencyId” type=“StringVectorType”/>    <xs:attribute name=“mediaStreamStructureId”    type=“StringVectorType”/>   </xs:extension>  </xs:complexContent> </xs:complexType> <!-- Whitespace-separated list of strings --> <xs:simpleType name=“StringVectorType”>  <xs:list itemType=“xs:string”/> </xs:simpleType>

A sub-representation may be embedded in a regular representation, and may be described by the element “SubRepresentation.” The element “Representation” may include the element “SubRepresentation.” The element “SubRepresentation” may describe properties of one or more media content components that are embedded in a representation. A representation and sub-representation may share common attributes and elements.

Semantics of the element “SubRepresentation” are described as follows:

The element “SubRepresentation” may have the following attributes:

-   -   “level” may specify a level of a sub-representation.     -   “dependency” may specify a set of sub-representations within a         representation in which sub-representations depend on in         decoding and/or presentation process, as a whitespace-separated         list of values of “level.”     -   “bandwidth” may be identical to the attribute “bandwidth” of the         element “Representation,” but may be applied to a         sub-representation.     -   “contentComponet” may specify a set of all media content         components that are included in a sub-representation, as a         whitespace-separated list of values of “id” of the element         “ContentComponent.”

The following Table 8 shows an XML syntax of the element “SubRepresentation.”

TABLE 8 <!-- SubRepresentation --> <xs:complexType name=“SubRepresentationType”>  <xs:complexContent>   <xs:extension base=“RepresentationBaseType”>    <xs:attribute name=“level” type=“xs:unsignedInt”/>    <xs:attribute name=“dependencyLevel” type=“UIntVectorType”/>    <xs:attribute name=“bandwidth” type=“xs:unsignedInt”/>    <xs:attribute name=“contentComponent”    type=“StringVectorType”/>   </xs:extension>  </xs:complexContent> </xs:complexType> <!-- Whitespace-separated list of unsigned integers --> <xs:simpleType name=“UIntVectorType”>  <xs:list itemType=“xs:unsignedInt”/> </xs:simpleType>

Hereinafter, common attributes and elements of the elements “AdaptationSet,” “Representation,” and “SubRepresentation” will be described.

1) The elements “AdaptationSet,” “Representation,” and “SubRepresentation” may have the following common attributes:

-   -   “profile” may specify a profile between associated         representation(s) conforming to media presentation profiles. A         value of “profile” may be a subset of a value in a predetermined         higher level of a document hierarchy (representation, adaptation         set, MPD). When “profile” is absent, the value of “profile” may         be inferred to be the same as in a next higher level of the         document hierarchy. For example, when “profile” is absent for a         representation, “profile” at an adaptation set level may be         valid for the representation.     -   “width” may specify a horizontal visual presentation size of a         video media type on a grid determined by the attribute “sar.”         When “sar” is absent, a width and height may be specified as if         a value of “sar” is “1:1.”     -   “height” may specify a vertical visual presentation size of a         video media type, on a grid determined by the attribute “sar.”     -   “sar” may specify a sample aspect ratio of a video media         component type. “sar” may be in the form of a string including         two integers separated by “:”. A first integer may specify a         horizontal size of encoded video pixels in arbitrary units. A         second integer may specify a vertical size of the encoded video         pixels in arbitrary units.     -   “frameRate” may specify an output frame rate of a video media         type in a representation. For example, when a frame or field         rate is changed, a value of “frameRate” may be an average frame         or half an average field rate over the entire duration of a         representation.     -   “audioSampleRate” may be either a decimal integer value         specifying a sampling rate of an audio media component type, or         a whitespace separated pair of decimal integer values specifying         a minimum sampling rate and a maximum sampling rate of the audio         media component type. A value of “audioSampleRate” may be in         samples per second.     -   “mimeType” may specify a MIME type of a concatenation of         initialisation segment.     -   “codecs” may specify codecs that are present within a         representation.

2) The elements “AdaptationSet,” “Representation,” and “SubRepresentation” may have the following common elements:

-   -   “FramePacking” may have an index of 0 to N, and may specify         frame-packing arrangement information of a video media component         type.     -   “AudioChannelConfiguration” may have an index of 0 to N, and may         specify an audio channel configuration of an audio media         component type.     -   “ContentProtection” element may have an index of 0 to N, and may         specify information on content protection schemes used for         associated representations.

The following Table 9 shows common XML syntax of the elements “AdaptationSet,” “Representation,” and “SubRepresentation.”

TABLE 9 <!-- Representation base (common attributes and elements) --> <xs:complexType name=“RepresentationBaseType”>  <xs:sequence>   <xs:element name=“FramePacking” type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“AudioChannelConfiguration” type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“ContentProtection” type=“DescriptorType” minOccurs=“0” maxOccurs=“unbounded”/>   <xs:any namespace=“##other” processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“profiles” type=“xs:string”/>  <xs:attribute name=“width” type=“xs:unsignedInt”/>  <xs:attribute name=“height” type=“xs:unsignedInt”/>  <xs:attribute name=“sar” type=“xs:string”/>  <xs:attribute name=“frameRate” type=“xs:string”/>  <xs:attribute name=“audioSamplingRate” type=“xs:string”/>  <xs:attribute name=“mimeType” type=“xs:string”/>  <xs:attribute name=“segmentProfiles” type=“xs:string”/>  <xs:attribute name=“codecs” type=“xs:string”/>  <xs:attribute name=“maximumSAPPeriod” type=“xs:double”/>  <xs:attribute name=“startWithSAP” type=“SAPType”/>  <xs:attribute name=“maxPlayoutRate” type=“xs:double”/>  <xs:attribute name=“codingDependency” type=“xs:boolean”/>  <xs:attribute name=“scanType” type=“VideoScanType”>  <xs:anyAttribute namespace=“##other” processContents=“lax”> </xs:complexType> <!-- Stream Access Point type enumeration --> <xs:simpleType name=“SAPType”>  <xs:restriction base=“xs:unsignedInt”>   <xs:minInclusive value=“0”/>   <xs:maxInclusive value=“6”/>  </xs:restriction> </xs:simpleType> <!-- Video Scan type enumeration --> <xs:simpleType name=“VideoScanType”>  <xs:restriction base=“xs:string”>   <xs:enumeration value=“progressive”/>   <xs:enumeration value=“interlaced”/>   <xs:enumeration value=“unknown”/>  </xs:restriction> </xs:simpleType>

A segment may have a defined format, and may be the smallest addressable unit described by an MPD.

A segment may be referenced by an HTTP-URL included in the MPD. The HTTP-URL may be defined as an <absolute-URI> according to RFC 3986. The HTTP-URL may have a fixed scheme of “http://” or “https://,” and may be restricted by a byte range when attribute “range” is provided together with the URL. The byte range may be expressed as “byte-range-spec” as defined in RFC 2616. The byte range may be restricted to a single expression identifying a contiguous range of bytes.

Segment information may be assigned to representations, through presence of elements “BaseURL,” “SegmentBase,” “SegmentTemplate” and/or “SegmentList.” The segment information may provide information on location, availability and properties of all of one or more segments included in a representation. In particular, information on the presence and location of initialisation, media, index and bitstream switching segments may be provided.

The elements “SegmentBase,” “SegmentTemplate” and “SegmentList” may be included in the element “Representation.” In addition, to express default values, the elements “SegmentBase,” “SegmentTemplate” and “SegmentList” may be included in the element “Period” or “AdaptationSet.” When either “SegmentTemplate” or “SegmentList” exists in a level of a hierarchy, the other element may not be present on a lower hierarchy level. The elements “SegmentBase,” “SegmentTemplate” and “SegmentList” may inherit attributes and elements from the same element on a higher level. When the same attribute or element is present on both levels, an attribute or element on a lower level may have precedence over the attribute or element on the higher level.

The element “SegmentBase” may include information that is sufficient, when only a single media segment is provided per Representation and a media segment URL is included in the element “BaseURL.” When multiple media segments are present, either the element “SegmentList” or “SegmentTemplate” may be used to share the multiple segment base information.

When a representation includes one or more media segments, either the attribute “duration,” or element “SegmentTimeLine” may be present.

A segment list may be defined by one or more elements “SegmentList”. Each of the elements “SegmentList” may include a list of elements “SegmentURL” for a consecutive list of segment URLs. Each of the segment URLs may include a media segment URL, and a byte range. The element “SegmentURL” may also include an index segment.

A segment template may be defined by the element “SegmentTemplate.” To create a list of segments, specific identifiers that are substituted by dynamic values may be assigned to segments.

The segment information may provide the following information:

-   -   Presence or absence of initialisation, index and bitstream         switching segment information.     -   HTTP-URL and possibly a byte range for each accessible segment         in each representation.     -   All valid segment URLs declared by an MPD.     -   For services with attribute “type” of an MPD indicating         “dynamic,” segment availability start time and segment         availability end time of each segment.     -   Approximate media presentation start time of each media segment         in a media presentation timeline within a period.

A segment element or a sub-element of the segment element may include the following attributes:

-   -   “duration” may specify a constant approximate segment duration.         All segments within element “Representation” may have the same         duration. However, a duration of a last segment within a period         may be different from the other segments.     -   “sourceURL” may specify a source URL part. “sourceURL” may be         formatted either as an <absolute-URI> according to RFC 3986.         “sourceURL” may have a fixed scheme of “http://” or “https://”         or as a <relative-ref> according to RFC 3986. For example, when         “sourceURL” is absent, element “BaseURL” may be mapped to the         attribute “sourceURL.” Additionally, when “sourceURL” is absent,         attribute “range” may be provided.     -   “range” may specify a byte range restricting the HTTP-URL. The         byte range may be expressed and formatted as a byte-range-spec         as defined in RFC 2616. For example, when “range” is absent, the         element may refer to the entire resource referenced in the         attribute “sourceURL.”

The following Table 10 shows an XML syntax of information associated with a segment.

TABLE 10 <!-- Segment information base --> <xs:complexType name=“SegmentBaseType”>  <xs:sequence>    <xs:element name=“Initialisation” type=“URLType”    minOccurs=“0”/>    <xs:element name=“RepresentationIndex” type=“URLType”    minOccurs=“0”/>   <xs:any namespace=“##other” processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>   <xs:attribute name=“timescale” type=“xs:unsignedInt”/>   <xs:attribute name=“presentationTimeOffset”   type=“xs:unsignedInt”/>   <xs:attribute name=“indexRange” type=“xs:string”/>   <xs:attribute name=“indexRangeExact” type=“xs:boolean”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType> <!-- Multiple Segment information base --> <xs:complexType name=“MultipleSegmentBaseType”>  <xs:complexContent>   <xs:extension base=“SegmentBaseType”>    <xs:sequence>     <xs:element name=“SegmentTimeline” type=“SegmentTimelineType” minOccurs=“0”/>     <xs:element name=“BitstreamSwitching” type=“URLType” minOccurs=“0”/>    </xs:sequence>    <xs:attribute name=“duration” type=“xs:unsignedInt”/>    <xs:attribute name=“startNumber” type=“xs:unsignedInt”/>   </xs:extension>  </xs:complexContent> </xs:complexType> <!-- Segment Info item URL/range --> <xs:complexType name=“URLType”>  <xs:sequence>   <xs:any namespace=“##other” processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“sourceURL” type=“xs:anyURI”/>  <xs:attribute name=“range” type=“xs:string”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType>  <xs:enumeration value=“progressive”/>   <xs:enumeration value=“interlaced”/>   <xs:enumeration value=“unknown”/>  </xs:restriction> </xs:simpleType>

Hereinafter, an additional configuration to select a representation based on a user characteristics and terminal characteristics will be described.

Based on the above-described solutions for DASH, representations may be described with various metadata. Characteristics of representations may be mostly used to select representations based on terminal characteristics, for example a resolution, a connection bandwidth, and the like.

Accessibility features of a representation may be used to support disabled users who have difficulties in perceiving multimedia content. The following embodiments to support accessibility may include 1) Moving Picture Experts Group (MPEG)-21 Digital Item Adaptation (DIA) accessibility description and 2) several hints used to facilitate enhancement/replacement of content components. In essence, the MPEG-21 DIA accessibility description including elements “VisualImpairmentType” and/or “AuditoryImpairmentType” of ISO/IEC 21000-7 may enable description of various symptoms of visual and auditory impairments of a user. The visual and auditory impairments may include, for example, a colour deficiency or low vision.

The following rule may be applied to URIs to identify specific accessibility schemes. For example, the schemes may be included in the above-described element “Accessibility.”

For representations containing audio and/or visual content, a URI may be defined as shown in Table 11 below.

TABLE 11 urn:mpeg:mpegB;dash:dash:mp21accessibility:<value>

The URI may be defined to indicate accessibility schemes based on accessibility description of ISO/IEC 21000-7.

For example, when <value> is “s0,” an appropriate representation may be prepared in advance, and an associated accessibility description may be described by the element “Accessibility.” Different ways may be used to convey the description. For example, the accessibility description may be either conveyed by element “MP21Access,” or referenced by attribute “xlink:href” that will be defined below.

When <value> is “s,” a provider may somehow obtain an accessibility description of a disabled user, and may provide appropriate content to the disabled user.

In the context of DASH, when a representation is associated with an accessibility description, the representation may be used for a disabled user whose specific symptoms are described by the accessibility description. Usually, media of the representation may be enhanced (e.g. adjusting contrast or colour) to cope with a problem of the disabled user. In this instance, the enhancement of the media may include, for example, adjustment of a contrast or adjustment of colour.

The above-described element “Accessibility” may be extended as follows. A new child element called “MP21Access” may be used as a container for MPEG-21 DIA accessibility description. Additionally, an optional attribute “xlink:href” may be added to the element “Accessibility” to reference an external description including MPEG-21 DIA accessibility elements.

Furthermore, a new attribute called “use” may be employed as a hint to let a client know the intended use of a representation, for the purpose of accessibility. The above new element and attributes may be applied to a representation group (or an adaptation set), a representation, and a sub-representation.

Semantics of elements and attributes to support accessibility are described as follows:

1) To support accessibility, the elements “Group”, “AdaptationSet”, “Representation” or “SubRepresentation” may further include the following attributes:

-   -   “use” may indicate an intended use of representation(s). The         attribute “use” may have values “signLang,” “subtitle,”         “caption,” “description,” “plusDesc,” and the like. The value         “signLang” may indicate a use as a sign language. The value         “subtitle” may indicate a use as a subtitle. The value “caption”         may indicate a use as a caption, namely, a subtitle with         additional description. The value “description” may indicate a         use as description, for example audio description of a movie.         The value “plusDesc” may indicate that content of a         corresponding representation is enhanced with description, for         example, may indicate a sound track enhanced with audio         description.     -   “xlink:href” may provide a reference to an external MPEG-21 DIA         description with elements “AuditoryImpairmentType” and/or         “VisualImpairmentType” of ISO/IEC IS 21000-7. The representation         or representation group associated with the description may be         suitable for disabled users whose problems are described by the         description.     -   “xlink:actuate” may provide processing instructions. The         processing instructions may be either “on Load” or “on Request.         When “xlink:href” is absent, “xlink:actuate” may not exist.

2) To support accessibility, the elements “Group”, “AdaptationSet”, “Representation” or “SubRepresentation” may further include the following elements:

-   -   “Accessibility” may have an index of 0 to N, and may provide         information on an accessibility information scheme.     -   “MP21Access” may have an index of 0 to 1, and may include         MPEG-21 DIA description with the elements         “AuditoryImpairmentType” and/or “VisualImpairmentType” of         ISO/IEC 21000-7. Representations or representation group         associated with the description may be suitable for disabled         users whose problems are described by the description.

The following Table 12 shows an XML syntax of the elements “Group”, “AdaptationSet”, “Representation” or “SubRepresentation”, to support accessibility.

TABLE 12 <!-- RepresentationBase type; extended by other Representation-related types --> <xs:complexType name=“RepresentationBaseType”>  <xs:sequence>   <xs:element name=“ContentProtection”   type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Accessibility” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Rating” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Viewpoint” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element    name=“MultipleViews” type=“MultipleViewsType” minOccurs=“0”/>   <xs:any  namespace=“##other” processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“group” type=“xs:unsignedInt”/>  <xs:attribute name=“width” type=“xs:unsignedInt”/>  <xs:attribute name=“height” type=“xs:unsignedInt”/>  <xs:attribute name=“parx” type=“xs:unsignedInt”/>  <xs:attribute name=“pary” type=“xs:unsignedInt”/>  <xs:attribute name=“lang” type=“LangVectorType”/>  <xs:attribute name=“mimeType” type=“xs:string”/>  <xs:attribute name=“startWithRAP” type=“xs:boolean”/>  <xs:attribute name=“frameRate” type=“xs:double”/>  <xs:attribute name=“maximumRAPPeriod” type=“xs:double”/>  <xs:attribute name=“numberOfChannels” type=“StringVectorType”/>  <xs:attribute name=“samplingRate” type=“StringVectorType”/>  <xs:attribute name=“use” type=“UseType”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType> <xs:simpleType name=“UseType”>  <xs:restriction base=“xs:string”>   <xs:enumeration value=“signLang”/>   <xs:enumeration value=“subtitle”/>   <xs:enumeration value=“caption”/>   <xs:enumeration value=“description”/>   <xs:enumeration value=“plusDesc”/>  </xs:restriction> </xs:simpleType> <!-- Generic named descriptive information about the content --> <xs:complexType name=“ContentDescriptorType”>  <xs:sequence>   <xs:element minOccurs=“0” name=“SchemeInformation”   type=“xs:string”/>   <xs:element minOccurs=“0” name=“MP21 Access”   type=“xs:string”/>   <xs:any  namespace=“##other” processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“schemeIdUri” type=“xs:anyURI” use=“required”/>  <xs:attribute ref=“xlink:href”/>  <xs:attribute ref=“xlink:actuate” default=“onRequest”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType>

Hereinafter, metadata describing a relationship between representations will be described.

There is little metadata for describing a relationship between representation groups. It is difficult for a client to know, for example, which video stream is associated with a given audio description. In several cases, two representation groups may be semantically equivalent, and only a single representation group may need to be selected based on a context. Hereinafter, two simple attributes are proposed for the above-described purpose. The metadata described hereinafter may be useful for accessibility as well as for adaptivity in general.

To describe the relationship between representations, the elements “Group”, “AdaptationSet”, “Representation” or “SubRepresentation” may further include the following attributes:

-   -   “usedWith” may indicate a list of one or more representations or         representation groups. When a current representation or a         current representation group is used, “usedWith” may be used         with a predetermined item of the list. For example, a         representation group for audio description may be used with a         specific representation group of a video component. A value of         “usedWith” may be a whitespace-separated list. Each item of the         whitespace-separated list may be identification of a single         representation group or a single representation. Identification         of a representation group may be a value of attribute “group” or         “adaptationSet.” Identification of a representation may have a         format of attribute “repid.” The attribute “repid” may be a         value of attribute “id” of the representation.     -   “equivalentTo” may indicate a list of one or more         representations or representation groups. A current         representation may be used instead of a predetermined item of         the list. For example, a representation group for a subtitle may         be used instead of a specific representation group of an audio         component. The attribute “equivalentTo” may have the same format         as the attribute “usedWith.”

The following Table 13 shows an XML syntax of the elements “Group”, “AdaptationSet”, “Representation” or “SubRepresentation”, to describe a relationship between representations.

TABLE 13 <!-- RepresentationBase type; extended by other Representation-related types --> <xs:complexType name=“RepresentationBaseType”>  <xs:sequence>   <xs:element name=“ContentProtection”   type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Accessibility” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Rating” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Viewpoint” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element   name=“MultipleViews” type=“MultipleViewsType” minOccurs=“0”/>   <xs:any  namespace=“##other”  processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“group” type=“xs:unsignedInt”/>  <xs:attribute name=“width” type=“xs:unsignedInt”/>  <xs:attribute name=“height” type=“xs:unsignedInt”/>  <xs:attribute name=“parx” type=“xs:unsignedInt”/>  <xs:attribute name=“pary” type=“xs:unsignedInt”/>  <xs:attribute name=“lang” type=“LangVectorType”/>  <xs:attribute name=“mimeType” type=“xs:string”/>  <xs:attribute name=“startWithRAP” type=“xs:boolean”/>  <xs:attribute name=“frameRate” type=“xs:double”/>  <xs:attribute name=“maximumRAPPeriod” type=“xs:double”/>  <xs:attribute name=“numberOfChannels” type=“StringVectorType”/>  <xs:attribute name=“samplingRate” type=“StringVectorType”/>  <xs:attribute name=“usedWith” type=“StringVectorType”/>  <xs:attribute name=“equivalentTo” type=“StringVectorType”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType> <!-- Type for space delimited list of strings --> <xs:simpleType name=“StringVectorType”>  <xs:list itemType=“xs:string”/> </xs:simpleType>

Hereinafter, metadata for bit depth will be described.

To select different representations for terminals having different display bit depths, the following attributes for a representation and a representation group may be used. A bit depth may refer to a number of bits used to represent a luma/chroma sample of visual content.

Semantics of attributes for bit depth are described as follows:

To provide a bit depth, the elements “Group”, “AdaptationSet”, “Representation” or “SubRepresentation” may further include the following attributes:

-   -   “bitDepth” may indicate a number of bits used to represent a         luma/chroma sample of visual content. When the bit depth varies,         for example, in different video pictures, a value of “bitDepth”         may be a maximum value of bit depths.

The following Table 14 shows an XML syntax of the elements “Group”, “AdaptationSet”, “Representation” or “SubRepresentation”, to support a bit depth.

TABLE 14 <!-- RepresentationBase type; extended by other Representation-related types --> <xs:complexType name=“RepresentationBaseType”>  <xs:sequence>   <xs:element name=“ContentProtection”    type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Accessibility” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Rating” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element name=“Viewpoint” type=“ContentDescriptorType”    minOccurs=“0” maxOccurs=“unbounded”/>   <xs:element   name=“MultipleViews” type=“MultipleViewsType” minOccurs=“0”/>   <xs:any  namespace=“##other”  processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“group” type=“xs:unsignedInt”/>  <xs:attribute name=“width” type=“xs:unsignedInt”/>  <xs:attribute name=“height” type=“xs:unsignedInt”/>  <xs:attribute name=“parx” type=“xs:unsignedInt”/>  <xs:attribute name=“pary” type=“xs:unsignedInt”/>  <xs:attribute name=“lang” type=“LangVectorType”/>  <xs:attribute name=“mimeType” type=“xs:string”/>  <xs:attribute name=“startWithRAP” type=“xs:boolean”/>  <xs:attribute name=“frameRate” type=“xs:double”/>  <xs:attribute name=“maximumRAPPeriod” type=“xs:double”/>  <xs:attribute name=“numberOfChannels” type=“StringVectorType”/>  <xs:attribute name=“samplingRate” type=“StringVectorType”/>  <xs:attribute name=“use” type=“UseType”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType> <xs:simpleType name=“UseType”>  <xs:restriction base=“xs:string”>   <xs:enumeration value=“signLang”/>   <xs:enumeration value=“subtitle”/>   <xs:enumeration value=“caption”/>   <xs:enumeration value=“description”/>   <xs:enumeration value=“plusDesc”/>  </xs:restriction> </xs:simpleType> <!-- Generic named descriptive information about the content --> <xs:complexType name=“ContentDescriptorType”>  <xs:sequence>   <xs:element minOccurs=“0” name=“SchemeInformation”   type=“xs:string”/>   <xs:element minOccurs=“0” name=“MP21Access”   type=“xs:string”/>   <xs:any  namespace=“##other”  processContents=“lax” minOccurs=“0” maxOccurs=“unbounded”/>  </xs:sequence>  <xs:attribute name=“schemeIdUri” type=“xs:anyURI” use=“required”/>  <xs:attribute ref=“xlink:href”/>  <xs:attribute ref=“xlink:actuate” default=“onRequest”/>  <xs:anyAttribute namespace=“##other” processContents=“lax”/> </xs:complexType>

Correspondingly, two attributes “minBitDepth” and “maxBitDepth” may be added to elements “Representation Group” or “AdaptationSet”.

Semantics of attributes to describe a maximum bit depth and a minimum bit depth are described as follows:

To describe the maximum bit depth and the minimum bit depth, the elements “Representation Group,” “Group,” or “AdaptationSet” may further include the following attributes:

-   -   “xlink:href” may indicate a reference to external element         “Group” or element “AdaptationSet”.     -   “xlink:actuate” may provide processing instructions. The         processing instructions may be either “on Load” or “on Request”.     -   “minBitDepth” may indicate a minimum bit depth value, in all         representations in a group or an adaptation set.     -   “maxBitDepth” may indicate a maximum bit depth value, in all         representations in a group or an adaptation set.

The following Table 15 shows an XML syntax of the elements “Representation Group”, “Group”, or “AdaptationSet”, to support the maximum bit depth value and the minimum bit depth value.

TABLE 15 <!-- Group to contain information common to a group;  extends RepresentationBaseType --> <xs:complexType name=“GroupType”>  <xs:complexContent>   <xs:extension base=“RepresentationBaseType”>    <xs:sequence>     <xs:element name=“Representation” type=“RepresentationType”      minOccurs=“0” maxOccurs=“unbounded”/>     <xs:element name=“SegmentInfoDefault” type=“SegmentInfoDefaultType” minOccurs=“0”/>    </xs:sequence>    <xs:attribute ref=“xlink:href”/>    <xs:attribute ref=“xlink:actuate” default=“onRequest”/>    <xs:attribute name=“minBandwidth” type=“xs:unsignedInt”/>    <xs:attribute name=“maxBandwidth” type=“xs:unsignedInt”/>    <xs:attribute name=“minWidth” type=“xs:unsignedInt”/>    <xs:attribute name=“maxWidth” type=“xs:unsignedInt”/>    <xs:attribute name=“minHeight” type=“xs:unsignedInt”/>    <xs:attribute name=“maxHeight” type=“xs:unsignedInt”/>    <xs:attribute name=“minFrameRate” type=“xs:double”/>    <xs:attribute name=“maxFrameRate” type=“xs:double”/>    <xs:attribute name=“minBitDepth” type=“xs:unsignedInt”/>    <xs:attribute name=“maxBitDepth” type=“xs:unsignedInt”/>    <xs:attribute   ame=“subsegmentAlignment” type=“xs:boolean” default=“false”/>    <xs:attribute name=“segmentAlignmentFlag” type=“xs:boolean”/>    <xs:attribute name=“bitStreamSwitchingFlag” type=“xs:boolean”/>    <xs:anyAttribute namespace=“##other” processContents=“lax”/>   </xs:extension>  </xs:complexContent> </xs:complexType>

FIG. 2 is a signal flowchart illustrating a content processing method according to an embodiment of the present invention.

A terminal 200 may be a DASH client described above.

The DASH client may be compatible with a client specified in RFC 2616.

The DASH client may typically use an HTTP GET method or an HTTP partial GET method, as specified in RFC 2616, to access segments or parts of segments.

A server 210 may perform hosting on DASH segments. The server 210 may be compatible with a server specified in RFC 2616.

In operation 220, the terminal 200 may receive metadata of media content from the server 210. In other words, the server 210 may transmit the metadata of the media content to the terminal 200. The media content may include one or more periods.

Metadata may be an MPD.

The MPD may provide sufficient information to the terminal to provide a user with a streaming service by accessing segments through a protocol specified in a scheme of defined resources. The specified protocol may be an HTTP/1.1. The server 210 may provide an MPD delivery function. The MPD may be generated based on DASH media presentation preparation.

In operation 230, the terminal 200 may process the received metadata. In operation 230, the terminal 200 may extract information provided by the metadata, or information included in the metadata.

In operations 240 through 250, the terminal 200 may access a segment of the media content based on the information provided by the metadata. The server 210 may be an HTTP server used to provide a DASH segment transfer function.

Each of the periods may include one or more groups, and each of the groups may include one or more representations of the media content. In other words, each of the periods may include the one or more representations of the media content. Accordingly, each of the representations may start from a beginning point of a period including each of the representations, and may continue to an ending point of the period. Each of the representations may include one or more segments.

In operation 240, the terminal 200 may send a request for a segment of the media content to the server 210 using a URL of the segment. The URL may be resolved with respect to the above-described element “BaseURL.” For example, the URL of the segment may be generated based on the element “BaseURL.”

The MPD may provide the terminal 200 with sufficient information to provide a user with a streaming service, by 1) requesting the server 210 to transmit segments, and by 2) demultiplexing, decoding, and rendering media streams included in a segment.

The terminal 200 may request the server 210 to transmit a segment suitable for a specific period based on the processed metadata. In other words, the requested segment may be selected based on the metadata. The terminal 200 may perform the HTTP GET method, to request the server 210 to transmit the segment.

The metadata may include an attribute “range”. The request may include a request for bytes of a resource indicated by a URL that are designated by the attribute “range.”

The URL of the segment may be an absolute URL or a relative URL.

The terminal 200 may select a period, an adaptation set, a representation, and the like, using an element or attribute included in the metadata, and may select a segment to be requested, based on an element or attribute of the selected period, the selected adaptation set, or the selected representation.

For example, each of one or more representations included in a period may include information used to support disabled users who have difficulties in perceiving media content. A media component of each of the representations may be enhanced to cope with a problem of a disabled user. Enhancement of the media component may include at least one of adjustment of a contrast and adjustment of colour. Additionally, information included in each of the representations may indicate an intended use of each of the representations. The intended use may include at least one of a sign language, a subtitle, a caption, and a description. The information included in each of the representations may include an attribute providing a reference to an external MPEG-21 DIA.

For example, metadata may include an attribute describing a relationship between one or more representations. A first representation among the representations may include an attribute indicating a list of a part of the representations. The first representation may be used together with a representation among the part of the representations. The first representation may be a representation used for audio description, and each of the part of the representations may be a representation used for a video component. Additionally, a second representation among the representations may include an attribute indicating a list of a part of the representations, and a representation among the part of the representations may be replaced by the second representation.

For example, each of one or more representations included in a period may include a bit depth attribute used to select different representations for terminals having different display bit depths.

The bit depth attribute may indicate a number of bits used to represent a luma/chroma sample of visual content.

In operation 245, in several cases, the server 210 may need to parse media content (for example, an MPEG layer 4 (MP4) file for Scalable Video Coding (SVC)), and may extract a data part suitable for the requested segment.

In operation 250, the server 210 may transmit, to the terminal 200, segments suitable for each request from the terminal 200. The terminal 200 may receive the segments from the server 210.

In operation 260, the terminal 200 may perform decoding and rendering on data of the media content included in the segment, to play back the media content.

The terminal 200 may play back the media content using the received segments by repeating operations 220 through 260.

Technical information according to the embodiments of the present invention described above with reference to FIG. 1 may equally be applied to the present embodiment. Accordingly, further description thereof will be omitted.

FIG. 3 is a diagram illustrating categories of signaling information according to an embodiment of the present invention.

The signaling information (namely, metadata) may be divided into the following categories 1) through 4):

1) General information 310: may include common description of content, and general description of each interval, such as a duration, and a start time.

2) Quality of Service (QoS) information 320: may describe characteristics of each alternative, such as a bitrate, a resolution, and a quality. In other words, the QoS information describes characteristics of each of alternatives of content.

An alternative may be physical (namely, created in advance), or may be virtual (namely, to be created on the fly). Based on information of alternatives, the client may select a fragment of an appropriate alternative. Accordingly, adaptivity to contexts of terminals and networks may be supported.

3) Mapping information 330: may describe locations to retrieve content. Depending on specific cases, different alternatives may have the same or different locations.

4) Client request 340: this type of signaling information may conform to a format of HTTP 1.1 request message. Parameters requested by a client may be derived from the information of categories 1) through 3).

FIG. 4 is a diagram illustrating a hierarchy of content division and levels of signaling information according to an embodiment of the present invention.

Signaling of metadata according to an embodiment of the present invention may be physically separated into content-level information 410, interval-level information 420, QoS information 430, and mapping information 440. Linking of related parts of the content-level information 410, the interval-level information 420, the QoS information 430, and the mapping information 440 may be performed by reference.

These parts of signaling information may be combined in different ways to support the flexibility.

For example, when only the content-level information 410 and interval-level information 420 are sent to a client, all computations for deciding alternatives and resolving locations may be performed by a server. Accordingly, when only the content-level information 410 and interval-level information 420 are sent to the client, a processing model may be “server-based.”

When the content-level information 410, the interval-level information 420, and the QoS information 430 are sent to the client, all computations for deciding alternatives and resolving locations may be distributed and performed by the client and the server. Accordingly, when the content-level information 410, the interval-level information 420, and the QoS information 430 are sent to the client, the model may be “distributed.”

When all the signaling information (namely, the content-level information 410, the interval-level information 420, the QoS information 430, and the mapping information 440 is sent to the client, the model may be client-based, because most (or all) processing (namely, computations for deciding alternatives and resolving locations) is performed by the client.

The separation of metadata parts may enable efficiency in storage and delivery. For example, during a session, metadata of the content-level information 410 may be sent once, and only the interval-level information 420 may be periodically updated. Similarly, a single file containing the QoSInfo 430 may be used for different intervals and different contents.

FIG. 5 is a diagram illustrating a configuration of a terminal according to an embodiment of the present invention.

A structure of a terminal 100 may represent logical components of a conceptual DASH client model.

The terminal 100 may include an access engine 510, and a media engine 520.

The access engine 510 may be a DASH access engine.

The access engine 510 may receive metadata (for example, an MPD) from a server 110.

The access engine 510 may form requests, and may issue the formed requests to the server 110.

The access engine 510 may receive content (for example, segments or parts of the segments) from the server 110.

The access engine 510 may provide the content to the media engine 520.

An output of the access engine 510 may include media (or a part of the media) of an MPEG container (for example, an ISO/IEC 14492-12 ISO base media file format, or an ISO/IEC 13818-2 MPEG-2 transport stream). Additionally, the output of the access engine 510 may include timing information used to map internal timing of the media to a timeline of a media presentation.

Additionally, the access engine 510 may perform functions of the terminal 200 that are described in operations 220 through 260 of FIG. 2.

The media engine 520 may play back the provided content. Specifically, the media engine 520 may output the media using the media and the timing information that are output from the access engine 510.

Technical information according to the embodiments of the present invention described above with reference to FIGS. 1 through 4 may equally be applied to the present embodiment. Accordingly, further description thereof will be omitted.

The method according to the above-described embodiments of the present invention may be recorded in computer-readable media including program instructions to implement various operations embodied by a computer. The media may also include, alone or in combination with the program instructions, data files, data structures, and the like. The program instructions recorded on the media may be those specially designed and constructed for the purposes of the embodiments, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD ROM disks and DVDs; magneto-optical media such as floptical disks; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, and the like. Examples of program instructions include both machine code, such as produced by a compiler, and files containing higher level code that may be executed by the computer using an interpreter. The described hardware devices may be configured to act as one or more software modules in order to perform the operations of the above-described embodiments of the present invention, or vice versa.

Although a few embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents. 

1. A method for providing media content, the method comprising: receiving metadata of media content, the metadata comprising one or more periods; accessing segments of the media content based on information provided by the metadata; and decoding and rendering data of the media content that is included in the segments, wherein each of the periods comprises one or more representations of the media content, and wherein each of the representations comprises information used to support disabled users who have difficulties in perceiving the media content.
 2. The method of claim 1, wherein a media component of each of the representations is enhanced to cope with a problem of a disabled user, and enhancement of the media component comprises at least one of adjustment of a contrast and adjustment of colour.
 3. The method of claim 1, wherein the information included in each of the representations indicates an intended use of each of the representations, and the intended use comprises at least one of a sign language, a subtitle, a caption, and a description.
 4. The method of claim 1, wherein the information included in each of the representations comprises an attribute providing a reference to an external Moving Picture Experts Group (MPEG)-21 Digital Item Adaptation (DIA).
 5. A method for providing media content, the method comprising: receiving metadata of media content, the metadata comprising one or more periods; accessing segments of the media content based on information provided by the metadata; and decoding and rendering data of the media content that is included in the segments, wherein each of the periods comprises one or more representations of the media content, and wherein the metadata comprises an attribute describing a relationship between the representations.
 6. The method of claim 5, wherein a first representation among the representations comprises an attribute indicating a list of a part of the representations, and is available together with a representation among the part of the representations.
 7. The method of claim 6, wherein the first representation is a representation used for audio description, and each of the part of the representations is a representation used for a video component.
 8. The method of claim 5, wherein a first representation among the representations comprises an attribute indicating a list of a part of the representations, and is replaceable by a representation among the part of the representations.
 9. A method for providing media content, the method comprising: receiving metadata of media content, the metadata comprising one or more periods; accessing segments of the media content based on information provided by the metadata; and decoding and rendering data of the media content that is included in the segments, wherein each of the periods comprises one or more representations of the media content, and wherein each of the representations comprises a bit depth attribute used to select different representations for terminals having different display bit depths.
 10. The method of claim 9, wherein the bit depth attribute indicates a number of bits used to represent a luma/chroma sample of visual content.
 11. A terminal, comprising: an access engine to receive metadata of media content, to receive segments of the media content based on information provided by the metadata, and to decode data of the media content that is included in the segments, the metadata comprising one or more periods; and a media engine to receive the data of the media content from the access engine, and to output the media content, wherein each of the periods comprises one or more representations of the media content, and wherein each of the representations comprises information used to support disabled users who have difficulties in perceiving the media content.
 12. The terminal of claim 11, wherein a media component of each of the representations is enhanced to cope with a problem of a disabled user, and enhancement of the media component comprises at least one of adjustment of a contrast and adjustment of colour.
 13. The terminal of claim 11, wherein the information included in each of the representations indicates an intended use of each of the representations, and the intended use comprises at least one of a sign language, a subtitle, a caption, and a description.
 14. The terminal of claim 11, wherein the information included in each of the representations comprises an attribute providing a reference to an external Moving Picture Experts Group (MPEG)-21 Digital Item Adaptation (DIA).
 15. A terminal, comprising: an access engine to receive metadata of media content, to receive segments of the media content based on information provided by the metadata, and to decode data of the media content that is included in the segments, the metadata comprising one or more periods; and a media engine to receive the data of the media content from the access engine, and to output the media content, wherein each of the periods comprises one or more representations of the media content, and wherein the metadata comprises an attribute describing a relationship between the representations.
 16. The terminal of claim 15, wherein a first representation among the representations comprises an attribute indicating a list of a part of the representations, and is available together with a representation among the part of the representations.
 17. The terminal of claim 16, wherein the first representation is a representation used for audio description, and each of the part of the representations is a representation used for a video component.
 18. The terminal of claim 15, wherein a first representation among the representations comprises an attribute indicating a list of a part of the representations, and is replaceable by a representation among the part of the representations.
 19. A terminal, comprising: an access engine to receive metadata of media content, to receive segments of the media content based on information provided by the metadata, and to decode data of the media content that is included in the segments, the metadata comprising one or more periods; and a media engine to receive the data of the media content from the access engine, and to output the media content, wherein each of the periods comprises one or more representations of the media content, and wherein each of the representations comprises a bit depth attribute used to select different representations for terminals having different display bit depths.
 20. The terminal of claim 19, wherein the bit depth attribute indicates a number of bits used to represent a luma/chroma sample of visual content. 